The invention relates to a method and apparatus for treating aqueous liquids, particularlY drinking water, for effecting deionization removal of contaminants. There have been numerous laboratory and commercial attempts in the past to produce safe and acceptable drinking water irrespective of the feed water source. These attempts include devices utilizing activated charcoal, distillation, ozone generators, reverse osmosis units, and ion exchange resins. While all of these devices are acceptable to a certain extent, none of them are capable of accomplishing the objective according to the invention.
Activated charcoal has demonstrated effectiveness in removing some organics, color, odor, and taste from drinking water. However, activated charcoal adsorbs rather than destroys the contaminants. Therefore, it has a limited life and must frequently be replaced. When not properly replaced it can serve as a breeding ground for bacteria and therefore contaminates the water it seeks to purify. It has been proposed to utilize silver with the activated charcoal to provide disinfecting power, however in practice silver is easily deactivated by colloidally suspended materials.
Distillation devices effectively reduce the ionic content of the water, but so much so that the water is usually tasteless. Also many volatile organic species are carried over in the distillation process and retained in the drinking water, and distillation is a cumbersome, energy intensive procedure which requires frequent cleaning of the distillation vessel.
Ozone generators are capable of oxidizing organic contaminants, and microorganisms, in water, but do not effect deionization. Also the generator to produce the ozone is a high voltage one.
Reverse osmosis units can effect deionization and thereby reduce the level of inorganics. However the waste stream with such units is relatively large, the water must be extensively pre-filtered before it reaches the units, and even with pre-filtration fouling from organics, bacteria, and other species often occurs. Such units also have a limited life and require significant cleaning and maintenance.
Ion exchange resins can effectively deharden water, but they do so by substituting other ions--usually sodium ions--which may be undesirable for health reasons. Also the resins act by removing, rather than destroying, materials so they must be replaced when their capacity has been reached; and they do not reduce the levels of organic contaminants or microorganisms.
According to the present invention it is possible to simultaneously deionize aqueous liquid, and remove the contaminants therein. According to the invention the deionization is accomplished via electromigration, while the degradation is accomplished on the surface of particles within the units. In the preferred embodiment, the device according to the invention comprises a bed containing particles--preferably a mixture of non-conductive particles and conductive particles such as sand and graphite particles. An anode is mounted on one side of the bed and a cathode on the other, and preferably, though not necessarily, the electrodes are separated from the bed by porous material, such as non-ionic, porous membranes. A voltage gradient is provided across the bed by the electrodes, and the liquid to be purified is caused to flow through the bed (preferably upwardly). Deionization occurs since the ions within the liquid (irrespective of their charge, or the balance of their charges) are attracted to the electrodes. Degradation of contaminants takes place at the surfaces of the particles.
A wide range of sizes of particles, and proportions of non-conductive to conductive particles, may be utilized within the scope of the invention. Typically the non-conductive particles will be sand (although a wide variety of other materials may be utilized), the sand particles having a size range between about 0.01-0.16 inches. The conductive particles preferably comprise graphite particles, which typically have a size range of about 0.3 mm-0.85 mm. The mixture of particles can range from 100% conductive particles to 100% non conductive particles. For most applications there will be between about 5-20%, by volume, of conductive particles, with about 7.5% conductive particles considered optimum.
In one particularly advantageous form of the invention, a countertop water purifier is provided which has a single housing mounting all of the components, with a feed reservoir at the top of the housing, and provision for receipt of a removable container under a spigot which discharges purified water from the unit.
It is the primary object of the present invention to effectively destroy or remove a wide variety of ions and organic contaminants from aqueous liquids, particularly drinking water, in a simple, workable, and cost-effective manner. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.